For zoom, 24-70L or 24-105L seems to be the most popular few options, I personally owned multiple copies of both and never like them. but that's just a personal preference thing.

For prime, may be consider the 35L. it's one of my "walk-Around" lens, I said "one of" because if I am carrying prime I normally carry more than one, mostly 3 at least, but the 35L/Zeiss 35 F2 is the one I normally have with me.